To most Arbites on lesser worlds, they would claim this would be above their pay grade. Herold however, would have no qualms about shooting those men for dishonoring the rank of the Adeptus Arbites. It was his duty as the keeper of law and peace that these Chaos filth be undone by his hand. As the Chimera opened up, the Krieger was kind enough to give him ample room to wrought the Emperor's will. 

The spawn of Chaos, a writhing tentacle monstrosity of terror, muscle, and warp-curse. It tore at the chunks of the Rhino with a mutated strength that could only be unholy in nature. Luckily, the high velocity guns and the psyker had it handled, it seemed. The teeming hordes of filth were another matter, a tide he and the Death Trooper were happy to stem. 

Herold took a fragmentation grenade and flung it past the initial mass of heretic turned troops. Seconds before the shrapnel tore through the horde, he bore his shield and unslung his shock maul. The weapon's power meter sang in its highest setting, the maul head glowing with power. With a grimace the likes of which appeared before bloody work was to be done, he advanced. 

His shield held aloft, he shove-jerked forward and knocked back a tide of the vermin, before sweeping his shock maul before him. The shock-enhanced melee weapon blew apart heads and limbs. His shield was then held before him before any counter attack could be made. Yet again he pressed forward and ended lives, causing a rift in whatever 'ranks' the foe might have.